Dario Franchitti was taken to the hospital after crashing on the last lap of the Grand Prix of Houston. / Chris Trotman, Getty Images

by Jeff Olson, Nate Ryan and Curt Cavin, USA TODAY Sports

by Jeff Olson, Nate Ryan and Curt Cavin, USA TODAY Sports

Four-time IndyCar champion Dario Franchitti suffered two broken vertebrae, a fractured right ankle and a concussion in a scary crash in which his car went airborne into the catchfence during Sunday's Houston Grand Prix.

Debris from his car vaulted into the stands, injuring 13 fans and an IndyCar Series official, according to the Associated Press. Two people are being treated at a local hospital.

The accident comes just 10 days shy of the two-year anniversary of the death of Dan Wheldon, who died when his head struck a post at Las Vegas Motor Speedway after sailing 325 feet through the air in a fiery 15-car wreck that caused the race's cancellation.

Franchitti's car became airborne as he tried to pass Takuma Sato on a fast portion of the course in Turn 5. The car went airborne and tore into fencing, which held. His No. 10 Honda came to rest back on the temporary street circuit around Reliant Park with the front end missing but with the tub portion of the chassis intact. E.J. Viso was also caught up in the crash.

Viso and Sato climbed from their cars unharmed.

Franchitti could be seen moving shortly after the car came to rest. At one point, he lifted his helmet's visor and appeared to be removing his gloves.

Team owner Chip Ganassi said on TV the four-time IndyCar champion was OK.

"He's talking. His ankle is a little sore. His back is a little sore. He's going to take a trip to the hospital, but he is OK," Ganassi said.

Later, Ganassi told USA TODAY Sports' Cavin he asked the 40-year-old Scotsman about his condition before being loaded into an ambulance.

Ganassi said Franchitti responded: "I don't know."

Actress Ashley Judd, who married Franchitti in 2001 though the pair separated earlier this year, thanked fans on Twitter for their prayers and tweeted that she and their dogs "are on our way."

Several IndyCar drivers also took to Twitter to send well-wishes to Franchitti and injured fans. Graham Rahal, who finished 18th, said the crash was "flat out scary."

"To be totally honest, when I came up on it I had a flashback to Vegas, but on a smaller scale," Rahal told USA TODAY Sports. "When I came through there, the amount of carbon fiber and debris was mind-boggling. I was just hoping everyone was OK at that point. There were parts and pieces everywhere."

In the season-opening Nationwide Series race at Daytona International Speedway in February, Kyle Larson's Chevrolet went airborne into the catchfence and scattered debris that injured 28 fans. The track reinforced its crossover gate fencing by adding cables before its NASCAR weekend in July, but debates still raged over further improvements.

The posts at Las Vegas are positioned on the inside of the fence meshing, and many IndyCar drivers, including Franchitti, lobbied tracks to move the poles outside the fence, while some suggested a complete overhaul was needed.

After the Nationwide crash at Daytona, Franchitti tweeted, "it's time @indycar @nascar other sanctioning bodies & promoters work on an alternative to catch fencing. There has to be a better solution."

Tony George, formerly the head of IndyCar and Indianapolis Motor Speedway, commissioned the development of the SAFER barrier a decade ago and said "it was always our plan (that) the next thing was to address the fence.

"Mostly I think we need to be focused on redirecting the cars back onto the race surface and not allow them to get hung up (and) entangled in the fence," George said last year. "We've got to come up with something that's elegant enough and allows some protection for the drivers as well as the fan."

George has described a system similar to the mesh netting that keeps stray pucks out of the crowd at hockey games, but perhaps as a plexiglass-style "curtain" that won't obstruct grandstand sightlines.

Last year, IndyCar introduced a redesigned chassis (which was tested by Wheldon and named for him --"DW12") that featured new safety enhancements. The tub was designed to provide more protection against debris entering the cockpit, which was made wider to aid in driver extraction. Energy-absorbing seat insets added padding beneath and behind the driver.

Perhaps most notably, a wider underwing and rear "bumper covers" were intended to reduce the risk of cars going airborne by touching wheels.

But in a May 2012 interview with USA TODAY Sports, Franchitti said, "the series has tried hard to do stuff with the new car, but I'm not sure they've made the progress."